The invention concerns an emergency driving device for motor vehicles.
Automatically shifting transmissions are being installed in motor vehicles to an ever increasing extent. Such transmissions include transmissions with stepless, changeable gear ratios, or transmission with stages, which shift under load or shift with interruption of traction. An electronic control unit is assigned to such transmissions, which chooses and activates an appropriate gear change. This choice is made with dependency on parameters of available power, driving mode, and transmission characteristics. Additionally, the driver can optionally choose one ratio change or a group of ratio changes by the use of a selector lever and/or a program switch.
The control and regulation of the transmission is dependent on and is influenced by the control of additional systems of the vehicle, namely an engine, a service brake or a retarder brake system. These systems possess, as a rule, their own electronic control units, which units, by means of data busses, communicate with one another and with the electronic transmission control unit. The interconnection of such data busses is designated a Controller Area Network (hereinafter called xe2x80x9cCANxe2x80x9d busses).
In case the transmission control drops out, because of a defect in the electronics, as a rule, emergency devices are provided with which it becomes possible to drive the vehicle away from the roadway with a limited operational capability, or even to drive the vehicle to the next repair station. Such an defect can, among other things, occur in the failure of a CAN-bus or its interface.
EP 0 431 538 B1 discloses an emergency device, by which, in case of failure, a certain specified ratio stage can be brought into action by means of a special solenoid valve. The valve is activated manually by means of a screw, whereby certain logical circuitry of the normal transmission in the central control unit is deactivated during the emergency switching.
EP 0 380 214 A2 makes known an additional emergency driving apparatus, which gives the driver the ability, if the usual electronic control unit, or the distribution cable has faulted, thus bringing about a case of emergency, to select a forward or a reverse direction gear ratio from the normally available gear ratios. The presupposition in this case, is, of course, that the shifting actuator can still function.
The road load, in the case of the known emergency driving devices, is very limited, since for the forward and reverse movement, respectively, only one gear is available, and the shift must be into this, as a rule in a stillstand of the vehicle.
Thus the purpose of the invention, is to enable driving to be continued and allowing shifting into a multiplicity of gears upon faulting of a CAN-bus or its corresponding interface.
In accord with the invention, the transmission control unit is connected to a service panel. In case of a defect in the selector lever, or its signal lines to the electronic control unit, such as the connections and CAN-bus, the control of the transmission can be carried out manually on the service panel. If the service panel is activated, then the interface of the selector lever at the electronic control unit is interrupted. This interruption continues as long as the service panel is activated. It is, however, also possible, in order to avoid a conflict of control, not to activate the service panel until the control unit of the transmission signals a corresponding failure.
The service panel possesses, advantageously, the necessary switching functions for the gear shifting, these functions being on/off, neutral, forwards, reverse, clutch in, clutch out, shift up, and shift down. With the aid of such a service panel, all available gears can be shifted through, even though this requires increased attention on the part of the driver. By this means, it becomes possible to continue travel even to a distant service station or to complete a homeward travel out of a foreign country.
There exist, fundamentally, two possibilities for connecting the transmission control unit, which is integral with the transmission, to control units of other systems of the vehicle. This is accomplished by a separate, transmission-specific CAN-bus, which is to be provided in addition to the vehicle-specific CAN-bus. Another way of accomplishing the same thing is by a single, common, vehicle-specific CAN-bus, which coacts with a central electronic control unit. If only the transmission-specific CAN-bus fails, the transmission control unit can be regulated by the said service panel and the shifting will operate in its normal automatic manner. However, if the vehicle-specific CAN-bus drops out, then the shifting can be made only manually by means of the service panel. For this purpose, the service panel possesses a number of shifting functions, which the driver can activate. In doing this, the driver makes use of, in the normal way, the information of a display apparatus which will show the state of the shift in the transmission, along with the engine RPM and a speedometer.
The service panel can be continually connected with the transmission control unit. In order to assure the panel""s availability and capability to function in case of an emergency, it is advantageous, to connect this in a releasable manner with the said control unit. If this is done, then in a normal situation, the service panel can be removed and protectively guarded in a safe place in the vehicle and made use of only in a case of need. In an advantageous manner, the service panel should be protected against dust and dampness by sealing in a foil. Storage would be preferred with the maintenance materials or the emergency tools of the vehicle.
So that the connection for the service panel can be checked by a regular diagnostic examination, it is advantageous to provide the service panel with a removable adapter, as long as the service panel is not included.